For many Americans, the word depression means more than economic or psychological problems. Under their homes or places of business, the ground is literally sinking. Parts of the Houston-Galveston region, for instance, have dropped as much as 8 ft. In California's fertile agricultural valleys, the sink rate has reached 1 ft. per year. Indeed, geological depression is so serious, reports the New York Academy of Sciences, that it has already caused millions of dollars in damage across the U.S. The toll has ranged from broken sewer lines and cracked pavements to an increased incidence of lowland flooding.
Such sinking, called subsidence by...